Posts Tagged ‘renewables’

We are collaborating with Dr Ben Hughes and his PhD students (John Calautit and Hassam Chaudhry) from the Univ of Leeds to study thermal and energy efficiency in our bamboo huts to assess comfortability of these as a low-cost housing solution. Bamboo huts can be upgraded to become residential dwellings, but also can be a handy resource in disaster aid and emergency relief situations for response teams in communities struck by the forces of nature.

Indoors testing rig at Heriot-Watt Univ, by Sean Paterson

Bamboo is a sustainable material which grows like a weed (in fact, it is a giant grass) and it is readily available in places like India, Bangladesh, Far East countries and South America. It grows fast (approx 30cm a day!!) unlike timber and it is ‘clean’ to dispose (versus high energy demanding materials such as concrete or steel, very expensive to produce).

[Nicolas Salort has finished his MSc project in Renewable Energies at Heriot-Watt University. This is a snapshot of his work]

Some plants, for example the sunflower, have an extraordinary ability: they can follow the sun during daylight hours to enhance their photosynthesis ratio.

This was the idea that inspired us. We wanted to investigate if sunflower-inspired solar trackers would enhance the energy collected by a solar panel during the day.

During the survey stage we learnt three things:

– Heliotropism: plants can control the angle of their leaves relative to the sun, control light absorption, and rate of photosynthesis. [This is different from phototropism, which is their ability to orientate themselves towards the light during growth].

– Heliotropism is not exclusive of sunflowers. Alfalfa, cotton, soybean, bean and lupine also show that feature. The movements of the plant are caused by an organ, the pulvinus, situated at the base of the leaf. It contains motor cells that can change their inner volume by the action of turgot and thus allow the leaf to move.

– It is not the sunflower head that moves following the sun, but the leaves!. And the perception of the light is a vector. This means that the leaves are able to sense if the light beams are normal to the lamina of the leaf or oblique to it. They show a 3-axis rotation that allows them to reposition so they remain perpendicular to sunrays at all times.

The design and construction of a prototype gave us great insight in order to assess what a sunflower could bring to the design of a solar tracker.

The 3-axis rotation and the perception of light as a vector were features incorporated into the design of our mechanical device.

The program adjusts the panel so that each photodiode receives the same amount of light.

To enable solar tracking ability, Nicolas used a quadrant photodiode with a two-fold purpose: 1) Obtain information about orientation of the light beam (whether this was parallel or not to the optical axis); and 2) to inform the system which direction the device should move to reinstall a parallel position.

Smart materials or those with tailored functionalities are not necessarily artificial materials, manufactured ad-hoc, made out of composites and intricate micro-architectures. Sometimes, the simplest ones are those that work!.

A Norwegian company has begun installing a 1.5MW prototype tidal-energy plant featuring turbines constructed with wooden blades. The full article can be found here.

“Hydra Tidal extols the use of wood for this application because it is naturally porous and homogeneous material – so it has better mechanical and hydrological characteristics than current conventional materials, such as composites and steel.”

Wooden turbine blades for windmills have been used in the past, notably by Hugh Piggott, who runs DIY workshops and has a very well populated personal website. The last project I’ve seen (by Robin Lovelace, Univ of Sheffield) generated a 500W vertical axis turbine. Not much, but you can probably boil your kettle for tea tonight with that!.